Well if U.S. stocks have an index, the U.S. dollar can’t be outdone. For currency traders, we have the U.S. Dollar Index (USDX).

The U.S. Dollar Index consists of a geometric weighted average of a basket of foreign currencies against the dollar.

Say whutttt!?! Okay before you fall asleep after that super geeky definition, let’s break it down.

It’s very similar to how the stock indices work in that it provides a general indication of the value of a basket of securities. Of course, the “securities” we’re talking about here are other major world currencies.

The US Dollar Index Currency Basket

The U.S. Dollar Index consists of six foreign currencies. They are the:

Euro (EUR)

Yen (JPY)

Pound (GBP)

Canadian dollar (CAD)

Krona (SEK)

Franc (CHF)

Here’s a trick question. If the index is made up of 6 currencies, how many countries are included?

If you answered “6”, you’re wrong.

If you answered “23”, you’re a genius!

There are 23 countries total, because there are 18 members of the European Union that have adopted the euro as their sole currency, plus the other five countries (Japan, Great Britain, Canada, Sweden, and Switzerland) and their accompanying currencies.

It’s obvious that 23 countries make up a small portion of the world but many other currencies follow the U.S. Dollar index very closely. This makes the USDX a pretty good tool for measuring the U.S. dollar’s global strength.

US Dollar Index Components

Now that we know what the basket of currencies is composed of, let’s get back to that “geometric weighted average” part. Because not every country is the same size, it’s only fair that each is given appropriate weights when calculating the U.S. dollar index. Check out the current weights:

With its 17 countries, euros make up a big chunk of the U.S. Dollar Index. The next highest is the Japanese yen, which would make sense since Japan has one of the biggest economies in the world. The other four make up less than 30 percent of the USDX.

Here’s something interesting: When the euro falls, which way does the U.S. Dollar Index move?

The euro makes up such a huge portion of the U.S. Dollar Index, we might as well call this index the “Anti-Euro Index”. Because the USDX is so heavily influenced by the euro, people have looked for a more “balanced” dollar index. More on that later though. First, let’s go to the charts!

How to Read the US Dollar Index

Just like any currency pair, the US Dollar Index (USDX) even has its own chart. Holler at the U.S. Dollar Index

First, notice that the index is calculated 24 hours a day, five days a week. Also, the US Dollar Index (USDX) measures the dollar’s general value relative to a base of 100.000. Huh?!?

Okay. For example, the current reading says 86.212. This means that the dollar has fallen 13.79% since the start of the index. (86.212 – 100.000).

If the reading was 120.650, it means the dollar’s value has risen 20.65% since the start of the index. (120.650 – 100.00)

The start of the US Dollar Index is March 1973. This is when the world’s biggest nations met in Washington D.C. and all agreed to allow their currencies to float freely against each. The start of the index is also known as the “base period”.

The U.S. Dollar Index Formula

This is strictly for the grown and geeky. Here is the formula to calculating USDX:

ow to Use the USDX for Forex Trading

I bet you’re wondering, “How do I use this USDX in my trading arsenal?”

Well, hold your trigger finger and you’ll soon find out! We all know that most of the widely traded currency pairs include the U.S. dollar. If you don’t know, some that include the U.S. dollar are EUR/USD, GBP/USD, USD/CHF, USD/JPY, and USD/CAD.

What does this mean? If you trade any of these pairs, the USDX can be the next best thing to sliced bread (or hamburger on a bun… or chocolate ice cream).

If you don’t, the USDX will still give you an idea of the relative strength of the U.S. dollar around the world. In fact, when the market outlook for the U.S. dollar is unclear, more often times than not, the USDX provides a better picture.

In the wide world of forex, the USDX can be used as an indicator of the U.S. dollar’s strength.

Because the USDX is comprised of more than 50% by the euro zone, EUR/USD is quite inversely related. Check it:

Next, take a look at a chart of EUR/USD.

It’s like a mirror image! If one goes up, the other most likely goes down. Will you look at that? It seems like the trend lines almost inversely match up perfectly. This could be a big help to those big on trading EUR/USD.

Some of our forex trading friends in the forums monitor the USDX as an indicator for EUR/USD. Hang out with them if you wanna learn more about using this index.

If the USDX makes significant movements, you can almost surely expect currency traders to react to the movement accordingly. Both the USDX and forex traders react to each other. Breakouts in spot USD pairs will almost certainly move the USDX in similar breakout fashion.

To sum it all up, forex traders use the USDX as a key indicator for the direction of the USD.

Always keep in mind the position of the USD in the pair you are trading.

For example, if the USDX is strengthening and rising, and you are trading EUR/USD, a strong USD will show a downtrend on the EUR/USD chart. If you are trading a pair in which the USD is the based currency, such as the USD/CHF, a rise in the USDX will most likely show a rise in USD/CHF charts like the one shown below.

Here are two little tips you should always remember:

If USD is the base currency (USD/XXX), then the USDX and the currency pair should move the same direction.

If USD is the quote currency (XXX/USD), then the USDX and the currency pair should move in opposite directions.